Gas turbine engines are known and typically include a fan delivering air as bypass air into a bypass housing and further delivering air into a core engine. Air in the core engine is directed into a compressor where it is compressed. The compressed air is then delivered into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate.
Recently, it has been proposed to increase the diameter of the fan to, in turn, increase bypass ratios, or the volume of air delivered as bypass or propulsion air compared to the volume of air delivered into the core engine. However, the ability to make this increase is somewhat limited by the packaging envelope available on an aircraft.
It has been proposed to replace a single large diameter with a plurality of fan rotors. However, the proposals for driving the plurality of fan rotors have deficiencies in general.